<!DOCTYPE html>

<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>外边距</title>
        <style type="text/css">
            .wrapper { border: 1px solid blue ; text-align: center ; }
            .wrapper span { border: 1px solid red ; margin: 15px 10px ; }
            .wrapper .inner { margin: 0 auto ; }
        </style>
    </head>
    <body>
        <div class="wrapper">
            <span class="first">中国</span>
            <span class="second">华夏</span>
            <span class="third">中华</span>
        </div>

        <div class="wrapper">
            <span class="inner">犯我中华者必诛之</span>
        </div>
    </body>
</html>